Borrowing Arrangements - Summary of Borrowings Available to the Company from Institutions (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Debt Disclosure [Line Items]
Amount of borrowings	$ 571,958
Federal Home Loan Bank—San Francisco
Debt Disclosure [Line Items]
Amount of borrowings	333,351
Federal Reserve Bank—San Francisco
Debt Disclosure [Line Items]
Amount of borrowings	138,607
Pacific Coast Bankers Bank
Debt Disclosure [Line Items]
Amount of borrowings	50,000
Zions Bank
Debt Disclosure [Line Items]
Amount of borrowings	25,000
First Horizon Bank
Debt Disclosure [Line Items]
Amount of borrowings	$ 25,000